Preparation of granular carbon.



J. c. LEB. PREPARATION 0F GRANULAR CARBON.

APPLIGATIOH runnin. as, 1913.

Patented Aug. 26, 1913.

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L( /yv was UNITED sTATEs PATENT oEEioE.

JOHN C. LEE, OF BROOKL-INE, MASSACHUSETTS.

PREPARATION OF GRANULAR CARBON. Y

Specification of Letters Patent.

Patented Auer. 26,1913.

Application filed March 29, 1913.' Serial No. 757,558.

To all whom it may concern.'

Be it known that I, JOHN C. LEE, a c itizen of the United States, residing at Brook- Granular carbon is used v'in the manu.

facture of microphonic ytelephone transmitters and is generally made by heating lfinely divided anthracite coal or some prepared substitute until it possesses the desired electrical resistance. As heretofore produced such particles of. granular carbon have been of unequal electrical resist- `ance due to the fact that in the heating process it `'Igree of heat for substantially 'the same was impossible to subject each of the particles to substantially the same del-:length of time and as no means was known rfor separating thev particles into groups after the roasting, each possessing substantially the same degree of electricalresistance, the result was not satisfactory. Heretofore, the heating or roasting process has been applied to the granular carbon contained in some receptacle, the heat being applied from without, in consequence of which those particles `in contact with the container and nearest to the heat receive more heat than those more distant, toward the center of the mass, and agitation of the mass did not serve to give to each particle, with certainty, its proper amount of heat for the proper length of time.

To secure a uniform product, which is essential Vfor the best results, the important factors which must be controlled are, first, the intensity of the heat;` second, the time during which the' heat is applied; and, third, the equal heatingfor an equal time of each particle. Y

My process consists in heating the finely divided anthracite coal or other suitable material by means of an electrical current of definite intensity, passing through the body of material itself and, at the same time, controlling the particles of the body of material, so that each particle is exposed to the current for a definite time.

In the drawings I have shown apparatus suitable for performing my process.

Figure lisfa plan and Fig. 2 a sectional elevation on line 2-2 of Fig. 1, of a simple form of apparatus; Fig.. 3 is a plan; Fig. 4 a side elevation and Fig. 5 a sectional elevation-on line 8-3 of Fig. 3; Figs. 3, 4 and 5 Ishow a specifically different form, from that shown in Figs. 1 and 2.

In the drawings two forms of roasting apparatus are shown for performing the process, that shown in Figs. 1 and 2 being a very simple structure while that shown in Figs. 3, 4 and 5, has more detailed provision for adjustment and regulation, whereby different materials may be treated ,and the result varied by the use of the adjusting means. The device shown in Figs. 1 and 2 consists of a chamber or shell, 1, open at the top and bottom and made of plumba-go or some other suitable electrical conductor.

This. conductor shell is mounted upon an annular throat, 2, of refractory material, such as tire-brick, the aperture in which is relatively narrow ascompa-red with the diameter of the interior of the upper shell, 1. This annulus, 2, of refractory material, is intended to be replaced when desired to give throats or passages of different'diameters and capacity. Beneath the tire brick annulus or throat a second ring, 3, of plumbago or other suitable electrical conductor is secured. The conductors 1 and 3 are connected by suitable wires, L, to a suitable source `of electrical energy g.

The device shown in Figs. 3, 4 and 5 is made up of a vessel made of refractory material such as fire-clay, divided intov an upper chamber aV and a lower chamber b, the upper and lower chambers being connected by a narrow throat c.` The upper chamber a is open at the top to allow the introduction of the material, M, to be treated and the escape of gases generated by the partial decomposition of the granull'ar carbon in the process` of treat-ment and the lower chamber, b, is provided wlth an opening d controlled by a gate -e for drawing of the roasted or prepared carbon M. Inserted in the upperand lower chambers and suitably vsustained are a pair of electrodes f,

l "preferably made of carbon, each connected to a suitablesource of electrical yenergy g by wires As shown in the drawing the electrodes are in line with each other andl with the throat e. If desired a gas cock z' may also be connected 'with the lower chamber so that under certain` conditions the roasting or treatment of the granular material can be conducted in an atmosphere of gas, intro-duced through the gas cock.

In usingl the apparatus shown in. Figs-3, 4 and 5 the material to be treated 1s placed in the chamber, a, and passes into the throat oc andthe lower chamber bby gravity, in the same manner that sand in an hour-glass goes from one chamber to the other. Electrical energy of a predetermined electromotive force being transmitted to' one of the electrodes, f, f', a current `is caused to pass between the 'electrodes through thebody of.

` at o will-depend uponthe electrical resistance, of the granular material and the seen thatv the column. of granular materialinthe throat c is reached throughout `its amount v. 'of current it conducts. It will,

therefore, be evident, that by controlling the -current from .the generating source the -heat y generated at c can becontrolled.

The durationv of the. heating process as applied to each particle of material is governed by the timetakenby each particlein passingfthrough the contracted opening from chamber a to chamber b and this may be controlled by regulating the'general flow of material through the apparatus by means of the gate e controlling the lower opening d of chamber 'b. In thls manner it will 'be ent-ire cross section as it passes through the throat and it is subjected to the heat, which A is controlled from the generator, for the desired length of time, by regulating the speed at which the granular material flows down-l ward under the action of gravity. As the material enters the throat in its raw or untreatedcondition it g'ives the maximum-resistance to the flow of the electrical 'current and as`it passes out at the bottom, beyond the reach ofthe current, it gives the predetermined resistance according to the extent to which the lvolatile matter has been driven olf and as each particle in the vcolumn of material in the-throat is subjected to subl stantiallythe same amount of heat for sub-A stantially the same amount of time it follows thatthe result must be a substantially uniform action on each particle. It is desirable of course that the finely comminuted ma* terial should be screened before being placed in the apparatus and that particles of a relatively uniformI size should be treated' together.

In using theapparatus shown in igs. 1

and 2 the material M to be :treated is placed in the chamber 1 and passes, Aby gravity,

through the throat c'of the hre-brick sec- 1 sol 3, 4 and 5. The control ofthe flow of ma-.

terial'may be attained by changing the section, 2, and substituting one having a larger o-r smaller throat, as desired, or other means of cont-rol may be supplied.` The roasted material is received below, in any suitable receptacle and is'cooled as it falls through the` l air, -into the same.' l I My preferred form is. thatshown in Figs. 3,4 and 5in which the control is at the eXit of. the -lowe-r chamber, the throat or exit there being governed by a suitable gate and having the same effect as' controlling the passage of the material at the throat c.

IA claim: y 1. An apparatus for preparing granular carbon, consisting of a chamber; a relatively narrow throat leading .from the lower part -of said chamber; means tocause an electrical current, when the apparatus is in operation, topass through the material only while in-said throat, wherebyl the granular .carbon may be exposed tothe electrical cur-v rent for a predetermined space of time whilev passing from the chamber.

.2. `An carbon', consisting of an upper and a lower chamber; a relatively narrow throat con-` nectingsaid chambers; means to cause an electrical current to pass through the ma'- terlal in said throat,when in operation; an

apparatus for preparing-granular i exit for the prepared 'carbon at the lower .part ofthe lower chamber, whereby the exit of the prepared carbon therefrom may bef controlled to controlv the movement of carbon particles through the throat in the pathof the electrical current. f i

` 3. An apparatus for preparing granular carbon, consisting of an upper and a lower chamber; a relatively narrow.r throat connecting Said chambers; an electrode in each chamber, eachada-pted to be connected to an electrical source; an exit opening for the prepared carbon, at the lower part of the chamber,v a gate to control said Qpening, whereby the lexit of the prepared carbon therefrom may be controlled to controlV the gn day of March, 1913.

. Witnesses:

movement of carbon particles` through.l the throat 'and the electrical current..

10 ed by me at Boston, Mass.-7 this 27th JOHN. o. LEEQ JOSEPH T. BRENNAN, EVERETT E. KENT. 

